Ignition apparatus



United States Patent() 2,933,631 y IGNITION'APPARATUS `James I. Logan, Unadilla, N.Y., assignor to Bendix Aviation Corporation, Sidney, N.Y., a corporation of Delaware This invention relates to electrical apparatus and more particularly to devices adapted `for use in creating sparks, such as in ignition systems for combustion engines and the'like. Y y i One v01|? Vthe objects of the present invention is tol pro-l vide a novelly constructed dev-ice ofthe above character embodying an annular spark gap. 'l

Another object of the invention is to provide a novel spark gap construction which may be readily assembled into a rigid unit without damaging .the relatively fragile insulation required.

StillV another object ofthe invention .is to provide a novel igniter plug of the long-reach type which is espef cially' adapted for use in the ignitionAsys-tem of So-,called jet orV gas turbine type engines. Y l

A further object is to provide a novel spark plug or igniter of the so-called shunted-surface gap'type adapted to spark at relatively low voltages.

' Another object is to provide a, sparking device which is novelly constructed to permit the circulationV of air therethrough to cool the same.

A still further object is to provide a novel spark gap device which -is so constructed and assembled as to permit the use of relatively fragile insulating material.

Another object is Vto provide a novel spark or ignitcr plug which has a relatively longv and efficient operating lifeunder the most severe operating conditions.

The above and further objects and novel features of the invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purposes of illustration only, and are not intended as a definition of the limits of the invention.A Y In vthe drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a sectional side elevation viewofone form of igniter or sparking plug embodying the present invenltion, the section being'taken in a longitudinal axis' thereof; Y

Fig. 2 is a bottom View of the device of Fig. 1, the same being taken in the plane of line 2-2; f

Fig. 3 is an exploded view of the nose or assembly of the device of Fig. l;

Fig. 4 is a section taken on line 4-4 of Fig. l;

Fig. 5 is an enlarged half sectional view showing parts spark Y gap plane containing the of the nose assembly of Fig. 1 in loosely assembled re- 1 lation; and, g

Fig. 6 is a sectional view showing a modification of the nose or spark gap assembly.

The embodiment of the invention illustrated in Fig. 1 of the drawings, by way of example, is in the form of a long reach igniter or spark plug, for use in a jet or gas turbine Vtype engine but the entire structure or features ithereof may be adapted to other uses, such as in the ignition systems for reciprocating engines, oil burners,

.and the like. AAs shown, theupper or sealed section of the structure is constructed in a known manner to precomprises a casing or shell 10 in which a tubular insula-y tor 11 is seated on a gasket 12 and held in position by a nut 14 that operatively engages threads cut on the inner surface of shell section 10.

An enlarged head portion of a central conductor 15 is seated on a shoulder in insulator 11 and extends downwardly through Athe latter. An input terminal member 16 extends into :the upper end of the insulatorY and fisV electrically connected to conductor 15 by a small wire 17. The remaining space within the insulator'is prefer-Y ably lled with an insulating mass 18 which functions as a gas seal and'Y means for holding the parts in as-t sembled rela-tion. Several suitable sealing compounds are known to the art. One which has been successfully used consists of a mixture of lead oxide and Pyrex glass. If an elbow is required for connecting a power supply lead, theV terminal member 16 may be supplemented by a plug' 19 and pin 20. To .properly position pin 20 in the housing elbow, a lixture is used. This is made possible by the telescopic relation of plug 19 in terminal 16 and the fact .that pin 20 is longitudinally slidable in the transverse passage rear the end of plug 19. Whenthe parts are correctly positioned by the fixture (not shown) silver solder may be used for joining the parts 16, 19 and '20 of the terminal together. A middle or guide section is provided for holding the elongated central conductor 15 against excessive vibra.a tion. VThis portionY of Vthe device comprises a shell section 21 which :is arcwelded or Yotherwise suitably secured to the lower end `of shell section 10. In some install-ations this middle portion of the device passes through the air intake passage of the engine and one or more ports 22 are provided for receiving air to be utilized in a manner and for a purpose-to hereinafter appear. The ports 22 are somewhat tangential as dis-1 tinguished from radial, so that the stream of air entering the shell is given a whirling motion.

In the lower end of shell section 21 is a tubular insulator 123 which' is seated upwardly against-` a ange 24 in the shell section and secured in 'positionby a ring 25 having a press'iit in said shell section;` A tubular guide 26 made .of metal or other'suitable materalis screw threaded in land rigidly supported by an internal ange in insulator 23 and closely surrounds conductor 15. Shell section 21 yis provided with an internal groove 27 and the upper surface of ring 25 has a radial-slot 28. The portion of insulator 23 which extendsjthrough ring 25 is of somewhat smaller diameter than Ythe'bore through said ring. Thus, air. may pass downwardly through and from shell section 21 by way' of groove 27,'slot 28`and the bore throughfring 25.V I .Y -f f 'i The end of shell section 21 and ring 25 are machined llush after assemblyand a spacer shell section 29 isfsecured thereto, such as by'arc Welding.' The Wall thickness of section 29 is sufficient to overlap ring 25'and thus secured, suclr as by arc welding, to Ithe lower end of shell 'g section 29. In the Vform shown, .the novel spark gap assembly which extends into the combustion chamber of the engine comprises a tubular shell section 30 having an end portion 31`of its bore tapered inwardly at a small angle toward the outer or lower' end thereof. Seated on and firmly engaging ltapered wall portion 31 is `a tapered outer or ground electrode 32 which, for purposes to here# nafter appear, is in the form of a split ring havingV a. plurality of axially extending slots 33. In one commercial embodiment ring 32 is 'longitudinally split at 34 Y(Fig. 3) and is provided with three slots 33.

An insulator 35 is similarly provided at oneend with Paienred Apr. 19, o

a tapered external wall which seats on the internal taperedV wallof electrode member 32. The lower or outer ends or extend slightly yb eyond the lower Yend face of shell section 30. Electrode 32V`may'be secured against movement relative toshell sectin 3i) and insulator'35 by any suitable means such Yas'p'ins 36 pressed into holes 38 in shell expands'the slotted lowerend of electrode 32 into firm `of insulator 35 and electrode 32 are preferably flush withl Y 30 to` engage notches 37 (Fig. 3) inthe electrode. The Y Y 41'and 43 are putY in place. Before substantial torque s pins may be secured in holes 38by staking. 1 Insulator 35 irs'secured and electrode 32 is further secured in position'in'shell section 30 by a ring 39 which has a-press fit in saidsection and engages the .upper` endV of the insulator. Ring 39 andshell section 3G are machined flush and arc welded toshellV section 29 which overlaps said ring and retains it` in assembled position. The lower edge of ring 39 has one or more radial slots 40 through which air may pass-from shell section 29 into the space around insulator 35 and thence throughthe passage formed between the retainin'gring 39 may bef threaded into shell section 30. :The center electrode of the spark'gap comprises a ring 41`shap`ed` like the frustruin of a coneto firmly engage and substantially full surface engagement with shell 30. At the same time the tapered outer surface of the insulator moves into rm and substantially fullsurface engagement with the inner surface of electrode 32. This desir-Y able ,result is thus accomplished without over-stressingV the insulator Vwhich is the'mostzfragileV of the parts. i'

The fixture is' now removed, and center electrode parts Y applied, initial contact between insulator wall 42 and elec-y trode 41 takes place at c, and the adjacent tapered sur;

faces diverge upwardly at an angle of about one-half degree.V When a force of about 5 inch/pounds is applied to member 43, the parts yield sufciently to give good surends (at 34) .of the split ring electrode 32." If desired, the ,Y

a' tapered portion 42 of the bore in the lowerndof nsu- Y d latdr 352 Electrode ring 41 is internally threaded and the small diameter end thereof is operatively engaged by an externally threaded'tubular member 43, the enlarged head portion of ,which seats on a tapered shoulder 44 in insulator 35 The surface'of member 43 which engages seat 44 is. preferablyspherical to facilitate properY seating of electrode 41 on seat 42. Conductor 15 extends through `nneruber 43 and is secured theretoat the end Vby any suitface contact between electrode 41 and the insulator.

Following the assembly as above described, the holes Y 38 and notches 3:7V aredrilled, and pins 36 are pressed into place.

The outer Vends Vofthe holes may then be stakedor pressed inwardly Vto hold the pins in position for locking electrode 32 against movementY relative to Vshell 30. -The lower vends of electrodes -32 and 41 are vthen Y ground ot to a plane which is flush with or withina maxi Ymumof about .O03 inch below the'plane of the. .eXPQCd The uppeend of kshell e endV face of insulator 35. y Y ring 39 are machined flush, ,and Vthe completed spark gap assemblypis arc welded to shell section 29. f VA modification o f-,the nose or spark gap assembly is illustrated'in Fig. 6. This structure differs from the em-Y y bodiment of Fig.Y 1 primarily in therfact that the shell is able means, such as by arc weldingor silver solder. Elee- Y e K y retainingring 52.` The latter may be threaded Vinto shell g 51,VV as shown, or may have a press tetherein. The center nace at a temperature of'vabout l,375 F. while a liquified petroleum'A gas containing essentially the propane hydrocarbon is flowed through the furnace. kCarbon may then be cleaned from surfaces fon which it is not desired by grinding or vapor blasting. It is permissible and desirable to` leave the carbon coating on the external and in-Y Y ternal tapered surfaces Vengaged by electrodes 32 andl41 and on the wall of the reduced bore through which merri-Y ber 43 extends.

tapered parts of the spark gap assembly, Ythe Vpartsf are Vnovelly constructed in relation toeach other and assembled under pressure in a novel manner. The relationship of the parts when looselyassembled and before the applicationjofany pressure isillustrated in Fig. 5.V Y

l fIn' assembling the nose ,or spark gap section, shell mem-Y bef 30 is placed ina fixture 45 (only partially shown) which, for the particular commerial embodiment here .described, permits the electrode 32-to project a maximum Y Vof about .040 inch beyond'the end `of the shell. Electrode 32 is then dropped into place in shell` 30 and the engagl, In order toinsure adequate surface contact between'the Y utilized as'theV ground electrode. As shown, a tubular insulator V50'isseated on'a tapered wallportion of the bore of a shell member 571'Yand is Vsecured in position by a electrode comprises an externally tapered'nut electrode 53 which ts a taperedrbore portion of the insulator and operatively engages a tubular, headed stud 54 through which centralfconductor 15 extends. The lower ends of shell 51, electrode 53 and stud 54 are ground off approxi mately ush with the end face of insulator 50, and parts 15,7573 and 54 are secured at their ends by arc welding or the likesV At-least the. exposed end face of the Vinsulator ductive material. Y A Y ,Y

In operation, input terminal 20 is connected to a source of electrical energy which preferably but 'not Vissemi-conductive or coated withV carbon or similar cona necessarily Vincludes facilities for high energy, low Voltage passes ythrough the semi-conductive or' carbon coated face of insulator 35,thereby ionizing the gases in the .vicinity and reducing the resistance to sparking soV that av high energy spark is created between the electrodes. 'e Spark- .e

ing may thus be insured at a relatively wide gap by a relatively low source of voltage, a phenomenon'which is Valreadyknown in the' art. If the end face of the insulaing tapered wall surfaces of the electrode and shell'areA zsuch 'that initialrcontact occurs at a and said surface diverges vdownwardly at an angle of about 1. vThe insulator 35 is then dropped into place and the engaging wall surfaces of electrode 324 and the insulator make initial'contact at b and said surfaces diverge upwardly at an n angle of about 1. Ring 39 which has a .003" press fitV in shell 30 is now pressed in and against insulator 35 with a pressure of about 1000 lbs. Electrode 32, being capable of closing in by reason of slot 34, moves downwardly withVV tor is burned away excessively, the 'device maybe reconditioned by; merely V'grinding down the endsOf-electrodes 32V and 41K.. f Y Y Although only a limitednumber ofv embodiments or modifications of the present invention have been illustratedyin the accompanying'drawings and described in the foregoing specification, it is to be expressly understood that the 'invention is notv limited thereto. t For example, the air cooling feature is not' essential` in some installa.- tion's and'm'ay be eliminated. VIn'suchinstallations, the Vsplit V34 in electrode ring 32 may be retained or'not, as

desired. Where shorter structures are required, thel middle or guide vsection for conductor 15 may be dispensed with and shell Ysection 30` attached directly Vto an extensioniof shell section 10.l Although electrodes 32 and 41 are Yshown ashaving substantially uniform wall thickness, either r both may have internal tapers whichv are greater or less than the external tapers thereof. Various otherchanges may also be made in the'design and arrangement of the parts illustrated lv'vithout departing from the spirit andiscope of the invention, as will now be understood kby those skilled in the art.

What is claimed is:

1. An electrical spark gap device comprising a tubular shell having a tapered boreV portion, a tubular insulator having an external wall portion tapered in the same direction as said tapered bore portion, a ring-like 'outer electrode wedged between said tapered portions of the shell and insulator, a center electrode in said insulator, the adjacent ends vof said electrodes'beingin spark gap relation across the annular end face of said insulator, and means for securing said shell, electrodes and insulator in assembled relation. a f

2.. A spark gap device as defined in claim 1V wherein said outer electrode isexpandable.

3. A spark gap device as defined in claim l wherein said outer electrode consists of a split ring, thereby rendering the same expandable.

4. A spark gap device as defined in claim 1 wherein said outer electrode has at least one axially extending slot therein to render the same expandable.

5. A spark gap device as defined in claim l wherein the center electrode comprises a cone-like member having the outer end thereof converging toward the outer end of said outer electrode.

6. A spark gap device as deiined in claim 5 comprising a member supported in the bore of said insulator and having threaded engagement with said cone-like center electrode member.

7. A spark gap device as defined in claim l comprising ,means for securing said outer electrode against movement relative to said shell.

8. An electrical spark gap device comprising a tubular shell having a tapered bore portion, a tubular insulator having an external wall portion tapered in the same direction as said tapered bore portion, a cone-like outer electrode wedged between said tapered portions of theV shell and insulator, a center electrode in the Vinsulator having spark gap relation with said outer electrode and at least one dowel extending axially in the wall of said shell and engaging said outer electrode to hold said outer electrode and shell against relative movement.

9. In electrical apparatus, such as a spark plug, a hollow shell having adjacent sections extending at an angle to each other, a lirst conductor centrally disposed in one section and insulated therefrom, said first conductor having a recess in the end thereof, a second conductor extending into said recess and having a transverse opening therein extending in the direction of the axis of the other section, and a third conductor extending through said transverse opening and along the axis of said other section, whereby said second conductor may he secured by soldering in said iirst conductor at a desired position and said'third conductor may be secured by soldering to said second conductor in a desired position.

10. Apparatus as defined in claim 9 wherein a cover is provided in an opening in said shell to afford access to joints between said conductors to permit adjustment and securing thereof.

ll. An electrical spark gap device comprising a tubular shell, an elongated centralV conductor means in said shell, means surrounding said conductor means at one end of the shell for insulating the shell from the conductor means, for tixedly holding the conductor means relative to the shell, and for forming a gas-tight seal between the shell and the conductor means, an electrode assembly mounted in the other end of said shell, and means mounted in said shell intermediate the ends thereof for centering said conductor means, said shell having an opening therein between said centering means and said irst-namedrmeans and said centering means atrone end of said shell for insulating the shell from the:` conductor means and forming a gas-tight seal therebe-V tween, an electrode assembly,comprisingelectrodes'in spark gap relation mounted in the other end of said shell, and means mounted in said shell intermediate the ends thereof for centering said conductor means in the shell, said shell comprising a plurality of sections joined together in endto-end relation, and said electrode assembly and each of said second-named and third named means being mounted in diiierent sections of the shell.

13. A spark device comprising a tubular outer elec trode having a tapered inner Wall portion, a tubu1arinsulator having an external tapered wall engaging said tapered wall portion and an oppositely tapered inner wall, and a center electrode in said insulator comprising a support member and an electrode member having anV vexternal tapered surface engaging said inner wall of the insulator, said support member and said electrode member having cooperating threaded engagement to wedge the latter into said insulator.

14. A spark gap device as dened in claim 13' comprising means for securing said insulator and outer electrode in assembled relation.

l5. Electrical apparatus comprising a tubular shell havv ing altapered bore portion adjacent one end thereof, a ring electrode seated on said tapered bore portion, said ring elctrode being internally and externally tapered, a tubular insulator having a tapered external wall seated in said ring electrode, said insulator having a bore portion within the tapered external wall thereof which is oppositely tapered, thereby providing the insulator With a narrow annular end face, a tapered center electrode seated in said tapered bore portion of the insulator, the adjacent end surfaces of said electrodes and said end face of said insulator being in approximately the same plane, means for securing said insulator and ring electrode in said shell, and means for securing said center electrode in the insulator.

16. A spark gap device comprising an outer electrode having a tapered internal wall, a tubular insulator having oppositely tapered external and internal walls at one end thereof to provide a narrow annular end face at said one end of the insulator, the tapered external wall of said insulator being seated against the tapered internal wall of said outer electrode, a center electrode having a tapered external wall portion seated against the tapered internal wall of the insulator, whereby the end faces of said electrodes are separated by said annular end face of said insulator, and means for securing said electrodes and insulator in assembled relation.

17. An electrical spark gap device comprising a tubular shell, an elongated conductor means passing through and centered in said shell, means surrounding said conductor means at one end of said shell for centering said conductor means in the shell, for holding it iixed with respect thereto, and for insulating the shell from the conductor and forming a gas-tight seal therebetween, and electrode Vassembly having opposed electrodes xedly held with respect to v each other and tixedly secured to the other end of said conductor means and to the other end of said shell, an insulating centering means mounted in said shell and contacting a portion of said conductor means intermediate the ends thereof, said shell having an opening therein between said centering means and said gas-tight seal, said centering means and said electrode assembly having passages therein for permitting the ow of gases longitudinally through said shell.

18. In a spark gap device as defined in claim 17 wherein'said shell comprises a plurality of sections joined esl, thsmerins means and the electod asssmbly @gather in end-torendf relation, and wherein the sast Yti reke-ach mounted inndiierent sections of the shell, Y t. Y19.- The method ofv making spark aapdsvcs which comprises making a tubular shell liavin7 a tapered internal VV x/,21111 portion, placing therein a Atapered ring-like electrode Iliaying at least jtheV smaller end thereof expansible, the Vtaper of the external Wall of said `electrode beingsucllV that the small end thereof diverges at a small angle fromV saidktapered wall' portionV of the shell, placing a tubular insulatgr-.in ,said shell and electrode, said insulator having oppositely tapering inner and outer Wall portions, said tapered outer Wall portion of the insulator diverging at a ksrnall angle from the inner Wall of said electrode at the larger end thereof, and pressing said insulator intoV said electrode to expand the latter into firm surface engagement with said shell and eiect iirrn surface engagement between said electrode `and insulator.

zorhe method desired in claim 19 wherein the axial assetti,

movement ttf ysaid elast,rodsl rslative to said. shell islimwsli by a lxture While assembly pressure isapplied to said sulatoring a tapered center electrode 'in theend ,ofV said insulator, the `tapered. outer wall of said center electrode being diverf gent with the inner tapered wall'of the insulator ,at a small angle .toW-ardrthe small diameter end thereof, and applying force to .said center electrode to press Vift into the tapered 10 bore of the insulator.

References Cited in the le of. this patentV t UNITED STATES PATENTS 

